In a letter shared exclusively with Mic, the star-studded group said it intends to “use the power of our voice and the power of our vote to defeat Donald Trump and the hateful ideology he represents.”

“When dangerous and divisive leaders have come to power in the past, it has been in part because those of goodwill failed to speak out for themselves or their fellow citizens,” the letter continues. “Some of us come from the groups Trump has attacked. Some of us don’t. But as history has shown, it’s often only a matter of time before the ‘other’ becomes me.”

MoveOn took to Twitter Tuesday to promote its latest initiative.

A few months ago, we launched a campaign to stop Donald Trump and his hate from reaching the White House. #UnitedAgainstHate

YouTube star Laci Green, who also joined the campaign against Trump, told Mic that the GOP presidential nominee appeals to the “darkest tendencies of Americans.”

“American progressives must step up right now. Defeating Trump is not a matter of getting the word out that he’s basically Voldemort,” Green said. “To defeat Trump, we need to get people, and especially young progressives, to actually vote in spite of frustrations with Clinton.”

Another celebrity signer is Michael Moore, who recently wrote a blog explaining the “5 Reasons Why Trump Will Win.”

I hate to be the bearer of bad news, but as things stand today, I think Trump will win. Here's my 5 reasons why: https://t.co/jotMPWmt96

In his column, Moore merely elaborated on comments he made during a special episode of Real Time with Bill Maher.

“The truth is, I’m sorry to have to be the buzzkill here so early on, but I think Trump is going to win,” Moore said last week during the Republican Nation Convention.

Letter-writing has become a popular way for celebrities to express their frustration with Trump.

In November, dozens of Hispanic cultural leaders signed an open letter published by Univision in which they decried the candidate’s “hate speech” that encourages “physical aggressions against Hispanics.”

“His hate speech appeals to lower passions like xenophobia, machismo, political intolerance and religious dogmatism,” the letter, signed by director Alejandro Inarritu and actor Diego Luna, read. “All of which inevitably reminds us of the past campaigns that have been directed against other ethnic groups and that have resulted in the deaths of millions of people.

In May, 400 authors — led by horror scribe Stephen King and Wild author Cheryl Strayed — penned an open letter to Trump in which they said they could not support his candidacy as a “matter of conscience.”

Earlier this month, 140 Silicon Valley-based technology executives signed an open letter claiming Trump would be a “disaster for innovation” as president, and asserting that “diversity is our strength.”